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H-bridge cascaded SVG parallel harmonic circulation suppression method

A technology of harmonic circulation and parallel connection, which is applied in the direction of harmonic reduction device, AC network to reduce harmonic/ripple, AC network circuit, etc. Problems such as disconnection

Active Publication Date: 2020-02-14
NORTHEAST DIANLI UNIVERSITY
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Problems solved by technology

However, due to the inconsistency of the initial phase parameters of the high-frequency carrier between parallel SVGs, a large amount of harmonic circulation is caused, which increases the harmonic content between parallel SVGs and affects the effect of reactive power compensation. One-way charging and discharging occurs, causing the recloser connected to the grid to be disconnected, causing the SVG to automatically withdraw from the system operation, and the power factor of the grid side drops instantly. It is difficult to eliminate and suppress these high-order harmonic circulating currents at the existing technical level

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[0034] The present invention assumes that there are n cascaded valve groups on each phase of each SVG, and the phase difference corresponding to each valve group carrier is fixed under the single-stage frequency multiplication carrier phase-shift modulation method (Set a bipolar carrier cycle as 2π), because the initial phases of different SVG carriers are different, resulting in phase deviation between the carrier of different SVGs and the SPWM control signal compared with even the same modulation wave, set each phase between two SVGs The overall carrier phase deviation angle of n in series is δ.

[0035] The steps are:

[0036] Step 1. Assume that the fundamental output voltages of the grid side and the three-phase A, B, and C phases of the SVG are completely symmetrical and run in a steady state;

[0037] Step 2. Directly change the triangular carrier frequency according to a certain time, reduce the phase difference of the parallel SVG carrier until the two carriers are ...

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Abstract

An H bridge cascaded SVG parallel harmonic circulating current suppression method, belonging to the technical field of electric energy quality analysis and control. The invention provides the H bridge cascaded SVG parallel harmonic circulating current suppression method and aims to suppress the parallel SVG circulating current with a simple and practical linear mode. The method comprises a step of setting the fundamental output voltage of A phase, B phase and C phase of a power grid side and an SVG to be completely symmetrical and run in a stable state, a step of directly transforming a triangular carrier frequency according to a certain time, a step of deducing the approximate range of a carrier phase through estimating the degree of the circulating current, a step of modulating a circulating current minimum value, a step of solving a problem by using a carrier frequency sweep time average deviation method, a step of verifying the validity of the steps, and a step of aligning the phases of all SVG carriers when the number of parallel is n. According to the method, the harmonic content between SVGs connected in parallel is improved, and a technical foundation is laid for the more mature elimination of harmonic circulation current between the SVGs connected in parallel in the future.

Description

technical field [0001] The invention belongs to the technical field of power quality analysis and control. Background technique [0002] Multi-parallel cascaded H-bridge static var generators (static var generators, SVG) have been obtained because they can improve the rapidity of dynamic var compensation, increase the capacity of reactive power compensation, and reduce the harmonic content of the system side. Wide range of applications. However, due to the inconsistency of the initial phase parameters of the high-frequency carrier between parallel SVGs, a large amount of harmonic circulation is caused, which increases the harmonic content between parallel SVGs and affects the effect of reactive power compensation. One-way charging and discharging occurs, causing the recloser connected to the grid to be disconnected, causing the SVG to automatically withdraw from the system operation, and the power factor of the grid side drops instantly. It is difficult to eliminate and sup...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H02J3/01H02J3/18
CPCH02J3/01H02J3/1857Y02E40/10Y02E40/40
Inventor 陈继开王泳权李江黄南天王鹤李扬王振浩
Owner NORTHEAST DIANLI UNIVERSITY
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